Everyone is assuming it's a Pro just because of the size, but Apple just put out a new Pro. There's no way they're coming out with another one right after. This is a MacBook, running on an iPad CPU (which are as fast as some Pro CPUs now). It'll be cheaper than any of the (touchbar) MacBook Pros. It has to be, because it won't run most of the software at first, just Apple software and stuff ported from the iPad with Catalyst (e.g. MS Office and Adobe iPad apps). Everything else will have to be rewritten to run on ARM CPUs, and that will take time.
This will sell because it's cheaper (~$1500) and lighter (~3lb, fanless, smaller battery) with a big screen. (There should be a ~13-inch as well). Apple has been telegraphing the difficult switch to ARM for years, and this 16-inch rumor (if true), just indicates that it's happening now.
Anyone who just bought a new MacBook Pro might want to hold onto it until this new MacBook can run more than just Apple and iPad software.